1. Field of the Invention
The present invention relates to a DSL (Digital Subscriber Line) communication method and apparatus that provides communications between a user model and an ISP (Internet Service Provider) router for DSL services by using an existing two-wire telephone line and an existing DSL communication technology.
2. Description of the Related Art
In recent years, the expectation for ADSL (Asymmetric DSL) services is increasing by rapid growth of the Internet services.
FIG. 1 shows the configuration of an ADSL system that uses a conventional communication method. In this ADSL system, a personal computer 11 for Internet Web access and a personal computer 12 for IP telephone service are connected to an ADSL modem 14 over an LAN at the user premises. The ADSL modem 14 is connected to an office-side DSLAM (DSL Access Multiplexer) 16 via an ADSL circuit.
In the ADSL system of FIG. 1, the ADSL modem 14 processes the various communication protocols for Internet connection. The DSLAM 16 carries out the multiplexing and termination of the ADSL circuit. The DSLAM 16 is connected to an ATM switch 18. The ATM switch 18 is connected to an ISP (Internet Service Provider)-site router 20 that is provided as an ISP access server. In the example of FIG. 1, the router 20 is installed for a specific Internet service provider ISP1. Generally, the router of this type is installed for each of various Internet service providers. The router 20 performs the routing of IP data, the user authentication for Internet connection and the protocol conversion. The user-site ADSL modem 14 is connected to the Internet by means of the router 20.
With the conventional ADSL service, it does not have the function to deal with IP data for Web access and IP data for IP telephone separately. For this reason, when the user wishes to use the IP telephone during Web access on a single ADSL circuit, it is impossible to assign the required channel to use the IP telephone as the channel is already used by the IP data for Web access. Thus, the conventional ADSL communication has a problem that the transmission of the IP telephone voice may be delayed or the noise in the IP telephone voice may occur.
With the conventional ADSL service, when a single ISP supports both the IP data for IP telephone and the IP data for Web access, a PPP (Point-to-Point Protocol) connection is established between the user-site ADSL modem 14 and the ISP-site router 20. It is necessary that there is the one-to-one correspondence between the VP/VC (virtual path/virtual channel) value assigned and the PPP connection. Then the mutual communication between the modem 14 and the router 20 is carried out to transmit and receive the IP data for IP telephone and the IP data for Web access. In this case, there is no difference in the header information of the ATM cell between the IP data for IP telephone and the IP data for Web access.
Therefore, the modem 14 and the router 20 recognize only the same VC value of the ATM cell for both the IP data for IP telephone and the IP data for Web access. It is impossible to give priority to the transmission of the IP data for IP telephone during the communication of the IP data for Web access. Especially in the DSLAM 16 and the ATM switch 18 wherein only the processing of ATM cell level is performed, if the ATM cell has the same VC value, the same processing must be performed.
FIG. 2 shows the configuration of another ADSL system which uses a conventional communication method.
Conventionally, one conceivable method for raising the quality of the IP data for IP telephone using the existing communication technology is that the two VC1/VC2 leased line connection between the modem 14 and the router 20 be used rather than using the PPP connection, as shown in FIG. 2. However, it is necessary to assign a global IP to the user who uses the leased line connection shown in FIG. 2, and the communication cost needed for the user to receive the ADSL service becomes highly expensive.